Kinetic Molecular Theory
Gas particles are tiny, far apart and in constant random motion.
About this topic
Kinetic molecular theory explains gas behaviour. Gas particles are in constant random motion, are very small compared with the distances between them, exert no forces on each other except during collisions, and collide elastically. The average kinetic energy is proportional to the absolute temperature (kelvin).
Pressure arises from particles hitting container walls, and more frequent or harder collisions mean higher pressure. Heating a gas raises the average speed, not all particles equally: a distribution of speeds exists, shown on a Maxwell-Boltzmann curve. At the same temperature, lighter molecules move faster on average, so hydrogen zips around faster than oxygen. Real gases deviate from the ideal model at high pressure and low temperature, when particle volume and attractions matter.
Example: air at room temperature has molecules moving at around 500 metres per second, yet the smell of perfume takes time to cross a room because of constant collisions. The theory explains why gases fill containers, compress easily, diffuse, and why a bicycle pump becomes hot.
Misconceptions are that particles stop at absolute zero (the theory predicts minimum motion, not none), that all gas particles travel at the same speed, and that collisions lose energy. Remember that temperature measures average kinetic energy.
Key ideas
- Collisions are elastic
- Temperature measures average kinetic energy
- Explains gas laws
Quick check
Use cases: where Kinetic Molecular Theory helps
- Homework: review the key idea behind Kinetic Molecular Theory before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Kinetic Molecular Theory without notes.
- Visual learning: play with the interactive lab to see how Kinetic Molecular Theory changes when you adjust its inputs.
- Teaching a friend: explain Kinetic Molecular Theory in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Kinetic Molecular Theory?
Gas particles are tiny, far apart and in constant random motion.
What will I learn in Kinetic Molecular Theory?
Collisions are elastic. Temperature measures average kinetic energy. Explains gas laws.
Is Kinetic Molecular Theory part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Kinetic Molecular Theory lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Kinetic Molecular Theory?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.